Definitions:

1. A hammer driven by compressed air. NOUN
   • She wore earplugs to protect her hearing from the loud noise of the jackhammer.
2. A pneumatic or electro-mechanical tool that combines a hammer with a chisel to break hard surfaces. NOUN
   • The construction workers used a jackhammer to break up the old sidewalk.
3. A portable percussive tool that combines a hammer and a chisel used to drill or break hard matter, and often used in demolition, construction, and excavation work. NOUN
   • The workers used a jackhammer to break through the concrete foundation of the old building.
4. A powerful tool used fro breaking up hard surfaces like concrete, asphalt, or rock. NOUN
   • The road crew brought a pneumatic jackhammer to remove the damaged section of the highway.
5. To use a jackhammer or behave in a way similar to a jackhammer. VERB
   • I jackhammered the pavement to break through the first layers.

Synonyms:

• air hammer
• demolition hammer
• hammer drill
• pneumatic drill